A technology is known, in which an evaporative cooling device and an air conditioner are used together for cooling an interior of a facility (e.g. sealed casing) accommodating a heat generating element such as an electronic device in order to reduce a load on the air conditioner and a running cost of the air conditioner. For example, Patent Document 1 (JP 3990490 B2) discloses a technology, in which an air conditioning load on an air conditioner can be reduced by radiating heat in an interior to an exterior via cooling a high temperature heat radiated from a device in the interior by an evaporative cooling device.
However, the interior of a sealed casing may not be cooled below a temperature of an exterior air by evaporative cooling, and in principle, it may be difficult for the evaporative cooling device to cool the interior below a temperature of a refrigerant in the evaporative cooling device. The temperature of the refrigerant in the evaporative cooling device is approximately equal to a sum of a temperature of the exterior and the temperature of the interior divided by two. Since the temperature of the interior of the sealed casing may not be cooled to an operation guaranteed temperature of the device disposed in the interior under a situation where the temperature of the exterior is above 30° C., an air conditioning device that is vapor compression type such as an air conditioner is necessary besides the evaporative cooling device, and a space for the air conditioning device is needed. Moreover, since the evaporative cooling device and the vapor-compression type air conditioner cool the interior air of the sealed casing, those are affected by a position of the heat generating element, for example, and accordingly a cooling efficiency may be low.